Data set 01
1958 Mullard Receiving Tubes
Published operating points and test conditions from this source.
SECTION 1
Diode
Application
Application
Signal detection
SECTION 2
Triode
Application
Application
AF amplification
Voltage - Triode (with diode, heptode or hexode) ·Diode-Diode-Triode
TDD2A
Directly heated battery double-diode triode combining detector and amplifier functions. Paired diodes provide signal and control-voltage rectification while the triode amplifies the recovered signal in accumulator-powered receivers.
Directly heatedCold cathodeCommon cathodeDissimilar
- Sections
- 3
- Base
- -
- Socket code
- B7
- Base pins
- 5
- Nominal heater
- 2 V / 120 mA
Description
Battery-operated double-diode triode with common filament for detector and amplifier service.
Socket description
Medium 7-contact
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- -
- Socket code
- B7
- Base pins
- 5
- Nominal heater voltage
- 2 V
- Nominal heater current
- 120 mA
- Parallel heater voltage
- -
- Parallel heater current
- -
- Series capable
- No
Terminal pinout
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
Section ratings
3 physical sections, each with unique specifications.
Section 1
Diode
X-ray radiationInterelectrode capacitances
- Max cathode current
- 0.2 mA
Mullard TDD2A first physical diode, assigned to AVC detection (pin 2). The directly heated common 2.0 V, 0.12 A filament serves both diodes and the triode. Diode maximum anode current 0.2 mA and peak inverse anode voltage 125 V; the latter is a peak reverse rating, not a continuous positive anode voltage. Both physical diodes are separately represented.
Section 2
Triode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 25000 Ω
- Transconductance
- 0.0012 S
- Amplification factor
- 30
- Max plate voltage
- 150 V
- Max plate dissipation
- 0.6 W
- Max cathode current
- 5 mA
Mullard TDD2A directly heated battery double-diode triode, using a common filament. Maximum triode anode voltage 150 V, plate dissipation 0.6 W and cathode current 5 mA. Typical gm 0.7 mA/V and internal resistance 43 kΩ at 90 V plate, versus gm 1.2 mA/V and resistance 25 kΩ at 135 V plate; amplification factor 30. Control grid uses a top cap; the five-pin base has the two separate diode anodes and filament connections.
Section 3
Diode
X-ray radiationInterelectrode capacitances
- Max cathode current
- 0.2 mA
Mullard TDD2A second physical diode, used as speech detector on pin 5. Separate diode shares the directly heated filament with the first diode and triode. Maximum diode anode current 0.2 mA; peak inverse anode voltage 125 V. Peak reverse rating is not a continuous positive anode limit.
Source-dependent data
Operating conditions by source
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.